Given this complexity of isoglosses, it is obvious the hypothesis that the various linguistic environments through which it has passed are reflected in the language of the Avesta, due to the same events as the Mazdean religion. It is probable that the first origin of the G ā th ā, which perhaps date back to the same preaching of Zarathustra, and of the more ancient Ya š t, both to be placed in eastern Iran, and with the spread of the prophet’s word towards the West, the language of this first nucleus has been adapted to the phonetics of the north-western dialects, not without, however, that there remains traces of the primitive redaction. Of course, once a linguistic tradition was formed for the Mazdean religion, later creations also found expression in it. This hypothesis, which in the current state of the Iranian dialectological documentation cannot be adequately illustrated with linguistic means, draws comfort from the tradition that places Zarathustra’s preaching in eastern Iran and from the geographical and mythological references that are contained in the Ya š t. In the Media, properly, the sacred texts of Zoroastrianism have received their present form; just as there the monotheistic doctrine of Zarathustra found that dualistic form which is the essential character of the Persian religion and at the same time all the ancient patrimony of myths, legends and rites that accompanies it. Remarkable is the fact that the most conservative part of the lexicon, that is the terminology referring to the conformation of the land, comes from the avestic from non-arian substratum and presupposes a mountain environment: zar š tva – “stone”, i š kata – “rock”, ta ē ra -, sta ē ra – “summit”, ā – “meadow”, t ū tuk- “mud”, pawr ā na – “mountain back”, va ē ma – “rock”, f í nkav- “mountain peak”, fraor ə pa – “mountain”; all terms that occur in the recent Avesta and not in the G ā th ā. Finally, it cannot be excluded that the linguistic form of the Avesta may have undergone modifications in the subsequent Arsacidic and Sassanidic redactions through which the current text has passed. For Iran 1997, please check aristmarketing.com.
The Avestan and the ancient Persian of the inscriptions do not belong to the same phase of development, since while the former retains on the whole an eminently archaic character (due to its character as a religious language), which puts it, for the Gathic at least, on the same level of the Vedic, the second appears already engaged in that profound change that will give the physiognomy to the medieval phase.
The greatest distance is of course between the gath. and the. pers. registr.; in this, in fact, in addition to the innovations that appear in av. rec. (loss of effectiveness of the law of aspirates, extension of the ending of the noun pl. in demonstrative pronouns to the acc. pl., the disappearance of the ancient gen. in – ṛ š in the stems in – r attested in the gath.), others there are some that do not appear in that one and that constitute manifest beginnings of the medieval phase. In the phoneticism the most important innovations have already been accomplished which will be the differential characteristic of the south-western Iranian dominion, and of the tendency to lose the postonic word ending there is a trace in the fall of the final consonants – t, – h (da – s), no. This trend is accompanied by the weakening that is already emerging in the categories of decline. In the nominal decline, the dat. and its functions were assumed by the gen., in the themes in – ā the gen.-dat.-abl. which is a unique form has also come to be confused with the loc.; in the themes in – or the instrument. got confused with the abl.; the abl. is always governed by ha čā “from” or by y ā t ā “up to”, the loc., with the exception of proper names, is always accompanied by the postposition ā ; of the dual only faint traces remain. Similarly in the verb there is a very marked tendency to a reduction from the Indo-Iranian system; the aorist is already not very vital and of the ancient system of the perfect only ā ha “was” (whose paradigm is the result of a mixture with the imperfect) and the oct. è a χ riv ā “can do”; the notion of the past is now expressed by means of the verbal adjective, generally without the use of copula, starting that formation of participle-preterite that will assert itself in the medieval phase; in the thematic formation there is already the prevalence of the type – aya that it will establish itself as unique in the Western domain; the preverb is no longer autonomous as in see. and in av., but it forms a single body with the verb; the infinitive formations so numerous in av., where the nominal character is still very much alive, are reduced to the single suffix – tanay av. -ϑ nai, m. pers. – tan and – i š n.